AC Equipment
Core concepts
Know the main equipment families: split and multi-split systems, packaged rooftop units, chilled-water fan coil units with air-cooled or water-cooled chillers, variable refrigerant flow systems, and evaporative coolers. Understand the difference between DX and chilled-water systems, and between air-cooled and water-cooled condensing. Learn the role of air-handling units - filters, coils, fans, dampers, humidifiers - and terminal devices such as VAV boxes and diffusers.
Equipment selection requires matching capacity at design conditions, checking sensible and latent performance, static pressure capability, electrical supply, and part-load efficiency metrics. For chillers, know COP and kW/TR; for unitary equipment, know EER and SEER. Understand compressor staging, variable-speed drives, and economizer operation.
Traps in questions
- Nominal tonnage is not capacity at your design conditions - always check the performance table at the actual entering wet-bulb and ambient.
- A larger unit does not always give better part-load performance; oversized units cycle and lose efficiency.
- Confusing EER (full load) with SEER (seasonal) and kW/TR for chillers.
- Forgetting that water-cooled chillers need a cooling tower and condenser-water pump, adding auxiliaries.
Rule of thumb
1 refrigeration ton = 3.517 kW = 12,000 Btu/h. A chiller at 0.6 kW/TR has a COP of about 5.9 (COP ≈ 3.517 ÷ kW/TR).
Worked example
A 100 TR chiller draws 60 kW. kW/TR = 60/100 = 0.6; COP = 3.517/0.6 ≈ 5.86. If a proposed unit claims 0.45 kW/TR at the same conditions, verify the rating conditions before accepting - the improvement may reflect different condenser-water temperatures.